Objective: Nutritional disorders affect growth in children. The present study aimed to assess the nutritional status and vitamin D levels in children by use of different nutritional assessment parameters via bioelectric impedance analysis. Methods: Two hundred and seventy-nine patients who applied to our general paediatrics outpatient clinic with various complaints, such as poor nutrition, obesity, weakness, fatigue, pain in the legs and a lack of adequate sunshine, were included in the study. Anthropometric measurements, body composition analysis data gathered with an In-Body 230 device, and bioelectric impedance analysis (BIA) data were assessed for all patients. The patients were grouped according to BMI SDS as lean, normal weight, overweight or obese. The subjects' 25(OH)D vitamin levels were obtained from laboratory recordings. Results: Of the patients, 44.1% (n=123) were female. The mean age was 10.0 +/- 3.6 (2-17) years. Of the patients, 18.6% (n=52) were lean, 47.3% (n=132) were normal weighted, 14.7% (n=41) were overweight, and 19.4% (n=54) were obese. The mean 25(OH)D levels of the lean, normal weighted, overweight and obese patients were 22.9 +/- 13.5 ng/mL, 25.8 +/- 11.8 ng/mL, 20.7 +/- 7.7 ng/mL and 17.9 +/- 9.7 ng/mL respectively. Levels of 25(OH)D were lower in the obese group than in the other groups, but this difference was not significant. The prevalence of obesity is increased in boys during adolescence, while 25(OH)D levels are decreased among girls. Conclusions: The evaluation of nutritional status and body fat composition via BIA may be a helpful and reliable method of preventing and treating childhood obesity and malnutrition.